Magnetic switch cartridge construction



Jan. 7, 1964 G. A. REESE v MAGNETIC SWITCH CARTRIDGE CONSTRUCTION FiledFeb. 8, 1960 United States Patent Ofiice 3,117,201 Patented Jan. 7, 19643,117,201 MAGNETIC SWITCH CARTRIDGE CONSTRUCTION Glenn A. Reese, CanogaPark, Calith, assignor to The Magnavox Company, Los Angeles, Calit., acorporation of Delaware Filed Feb. 8, 1960, Ser. No. 7,473 7 Claims.(Cl. 20087) This invention relates to magnetic switches and, moreparticularly, to such switches which are fast-operating and reliable.

A magnetic switch is operated by a changing magnetic field which movesthe magnetic armature, and the movement of the armature transfersconductive connections through the armature from a first contact to asecond contact. The armature then forms part of the electrical circuitrythrough the switch. There are many applications which require high speedswitch operation for switching relatively small potentials measured inmicrovolts. Conventional magnetic switches are generally unsatisfactoryfor such applications because of speed limitations, and because of noiseintroduced through the capacitive coupling formed by the armature andthe surounding switch components. When small potentials are beingswitched, a relatively minute bounce of the armature as it engages astationary contact introduces noise of a magnitude corresponding to thatof the potentials being switched. This later bounce difficulty isemphasized with high speed and rapid armature movement.

To illustrate applications in which the switch requirements are fairlystringent, in my copending patent applications Serial Nos. 652,968,filed on April 15, 1957 now Patent No. 2,945,931; 753,041, filed onAugust 4, 1958 now Patent No. 2,988,616; and 813,736, filed on May 18,1959 now Patent No. 3,05 1,80 6, magnetic switching assemblies aredisclosed in which each of the magnetic switches is operated andreleased during intervals measured in microseconds. The switchingassemblies, moreover, are utilized for switching or sampling smallpotentials. Any noise introduced by contact bounce, by capacitivecoupling or otherwise, would be deleterious. Moreover, in theseswitching assemblies, rapid switch operation is required to provide forsampling interval accuracy. Variations in the speed of operation of themagnetic switches would materially vary the sampling intervals becausethe entire interval or channel during which a switch is opera-ted andthen reset is measured in microseconds.

In a specific illustrative embodiment of this invention, a magneticswitch is provided which may be utilized in the switching assembliesdisclosed in the above-identified patent applications or in otherapplications where high speed, reliable, substantially noise-free,operation is required. In the illustrative embodiment, a magnetic switchis provided which has an armature electrically isolated from thecontacts of the switch. The armature is not included as part of anyelectrical circuit through the switch. The armature may, therefore, beelectrically grounded to avoid any noise producing capacitive effect.Moreover, any deleterious effects resulting from a contact between thearmature and any of its surrounding components are avoided.

The armature supports a substantially cylindrical but slightly taperedarmature contact by means of a contact insulator which separates it fromthe armature. When the switch is assembled, the operation of the switchmay readily be adjusted by moving the armature longitudinally in theswitch to vary the longitudinal position of the tapered armature contactin the switch. The armature contact is positioned centrally among fourcontact segments. The four contact segments form an essentially diamondshaped internal surface about the armature contact. When the switch isnormal, the armature contact engages two of the contact segments, and,when the switch is operated by magneticaly influencing the armature, thearmature contact engages the other two contact segments.

Features of this invention pertain to the provision of predeterminedangles for the contact segments so that the armature contact does notbounce and the operating tolerances are quite small. The distancesbetween the opposite internal surfaces of the four segments areidentical and the armature contact can never simultaneously engage apair of opposite internal surfaces. One pair of opposite segments isconnected to simulate the common or armature electrical connection andthe other pair of opposite segments electrically represents respectivelythe open and closed conditions of the switch. Effectively, the switchsimulates a transfer contact wherein an armature is positioned tocontact one or the other of two associated contacts.

Other features of this invention relate to the dimensions of thesegments and of the armature contact such that the open and closedtransfer contacts can never be electrically connected in the switch.Even though the switch is subjected to considerable shock and vibration,at no time can the contact armature engage simultaneously the twoopposite contact segments which electrically form the transfer contactsof the switch.

Further advantages and features of this invention will become apparentupon consideration of the followiing description when read inconjunction with the drawing wherein:

FIGURE 1 is a sectional view of the magnetic switch of this invention;

FIGURE 2 is an exploded view of the magnetic switch illustrating thearrangement of its various components with portions of some of thecomponents removed;

FIGURE 3 is a partial sectional view of the contact segments and thearmature contact utilized in the magnetic switch of this invention; and

FIGURE 4 is a functional electrical representation of the magneticswitch of this invention.

Referring to FIGURES 1 through 4, a fast operating magnetic switch 10has an upper cylindrically-shaped shell 11 and a lowercylindrically-shaped shell 12 together forming a casing for the magneticswitch 10. The two shells 11 and 12 have substantially similar outer andinner diameters and may be of magnetic material such as steel to form amagnetic shield for the components enclosed therein. The shieldingfunction of the shells 11 and 12 is hereinafter described. The twoshells 11 and 12 may be welded together to form a single compositecylindrical casing. At one end of the magnetic shell 12 is affixed anarmature casing 13 which is preferably also cylindrical in shape and isadapted to be fitted into the end of the shell 12. The armature casing13 is non-magnetic and may, for example, be of brass to permit magneticflux through the casing 13 to a hollow armature 15 enclosed thereby. Thearmature 15 is made of magnetic material such as steel and is preferablycylindrical in shape, being fitted in the armature casing 13. Aninsulating collar 18 is mounted at one end of the armature 15 forpivotable movement with the armature 15. The insulating collar 18 has anouter diameter which is slightly greater than that of the armature 15and less than the inner diameter of the armature casing 13.

The armature 15 and the collar 18 are supported on a resilient wire 16which may be made of steel. The steel wire 16 is supported by a plug 17which is fitted at one end of the armature casing 13. The plug 17 may bemade of magnetic or nonmagnetic material and it may be made ofconductive or insulating material. The

plug 17 need not be made of insulating material because, as ishereinafter described, the armature 15 does not form part of theelectric circuitry through the switch 10. The armature casing 13 isfilled with a viscous oil which forms a cushion for the magneticarmature 15. A thin layer of oil is formed between the insulating collar18 and the inner surface of the armature casing 13. This layer of oilforms a dynamic pivot for the magnetic armature relative to the armaturecasing 13 with the collar 18 functioning as the fulcrum. As describedabove, the armature may be made of steel and the collar 18 may be madeof an insulating material. The collar 18 may also be made of aconductive material, as the armature 15 need not be insulated from thearmature casing 13 because it does not form a part of the electricalcircuits through the switch 10. Though the collar 18 and plug 17 may bemade of conductive material, in the specific illustrative embodiment,these components are made of insulating material to reduce the couplingbetween the casing 13 and the active components in the switch.

At one of its ends, the armature 15 supports the collar 18, and at itsother end it supports a contact insulator 20 illustrated particularly inFIGURE 2. The contact insulator 20 is a double plug member fitting onone side into the hollow armature 15 and on its other side into anarmature contact 22 which is supported thereby. The armature contact 22,which may be made of conductive material such as gold, is circular incross section, but slightly tapered (approximately a degree taper) awayfrom the armature 15. Due to the contact insulator 20, the armaturecontact 22 is insulated from the armature 15.

The tapered armature contact 22 fits among, and is encircled by fourcontact segments 24 through 27 of a contact disc 23. The position of thearmature contact 22 relative to the four segments 24 through 27 isillustrated particularly in FIGURE 3. In the normal position of thearmature 15, the contact 22 is in electrical contact with the twosegments 27 and 26 and, when the armature 15 is in its operatedcondition under the influence of a magnetic field through the casing 13,the contact 22 is in electrical contact with the two segments 24 and 25.The stroke or movement of the contact 22 between the pairs of segmentsmay be quite small, illustratively 0.001 inch. The spacing illustratedin FIGURE 3 is somewhat exaggerated to illustrate that the contact 22 isan electrical contact with only one pair of the four segments 24 through26. The length of the stroke may be adjusted when the switch isassembled by moving the armature 15 longitudinally in the armaturecasing 13. Due to the taper of the armature contact 22, its longitudinalmovement with respect to the disc 23 varies the spacing between it andthe segments 24 through 27.

The minimum distance between the two segments 25 and 27 is substantiallyequal to the minimum distance between the two segments 24 and 2s so thatthe armature contact 22 cannot simultaneously electrically contact apair of opposite segments. For example, the contact 22 can never besimultaneously against the segment 25 and the segment 27 because thedistance therebetween is greater than the diameter of the armaturecontact 22 at its cross section position in the disc 23. This particularconfiguration functions as a safety measure to prevent electricallyconnecting the two effectively stationary contacts of the switch whichare depicted in FIGURE 4.

As indicated in FIGURE 4, the switch 10 has two stationary contacts 50and 51 and a movable armature 52 which is normally positioned againstthe stationary contact 50 and which can be moved adjacent the stationarycontact 51. The safety measure provided by the particular configurationof a disc 23 and the armature contact 22 avoids establishing anelectrical connection between the two stationary contacts 50 and 51 atany position of the armature 22, even in the presence of shock orvibration of any magnitude. The two stationary contacts 5t) and 51 cannever be electrically interconnected because the diameter of thearmature contact 22 at the disc 23 is smaller than the distance betweenopposite pairs of the segments of the disc 23.

The contact segments 24 through 27 may be gold plated and may be formedas one continuous disc 23 which is brazed on one end of a ceramicinsulator 35). The centrally located diamond shaped opening in the disc23 is formed by an accurate punch die before the disc 23 is affixed tothe insulator 30. After the disc 23 is brazed to the insulator 30, thedisc 23 and a portion of the ceramic insulator 35) are cut to form theelectrically isolated segments 24 through 27. The ceramic insulator 30may be cylindrically shaped having a maximum diameter which issubstantially the same as the maximum diameter of the disc 23. Theceramic insulator 30 has a small cylindrical opening 30a at the end towhich the disc 23 is affixed so that the armature contact 22 can beinserted partially therein if necessary. The ceramic insulator 30 fitssnugly into the steel shells 11 and 12, which were described above,having a maximum diameter slightly smaller than the inside diameters ofthe shells 11 and 12. When the ceramic insulator 30 is manufactured,four cylindrical holes are formed through the insulator 30 having axesparallel to the longitudinal axis of the ceramic insulator 30. The endof the ceramic insulator 30 adjacent the disc 23 and the surfaces of thefour holes 40 are then metalized by a plating process.

When the disc 23 is cut to form the four segments 24 through 27, the endof the ceramic insulator 30 adjacent thereto is also cut to cut itsplated metallic surface. In this manner, the four segments 24 through 27are insulated from each other having no conductive connection across themetallic surface on the end of the ceramic insulator 30. The fourcontact segments 24 through 27 are oriented on the ceramic insulator 30so that an electrically conductive connection is made from each of thesegments 24 through 27 to one of the metalized holes 40 in the insulator30. At the other end of the four metalized holes 40 are inserted,respectively, four wires 34 through 37 which provide for electricalconnections to the magnetic switch 10. The four wires 34 through 37extend through an opening 11a at the end of the steel shell 11 asindicated particularly in FIGURE 1. In this manner, four electricalconnections are provided respectively through the four wires 34 through37, the four metalized surface holes 40 to the four segments 24 through27 of the contact disc 23.

This particular method of fabricating the switch components isrelatively inexpensive and yet, as is hereinafter described, the timingaccuracy and speed provided by the switch 10 are quite high.

As described above and indicated in FIGURE 3, the armature contact 22 isnormally positioned to provide electrical connection between the twosegments 27 and 26. When a magnetic field moves the armature 15, thearmature contact 22 is moved to provide a connection between the othertwo segments 24 and 25. As also described above, the distances betweenthe opposite internal faces of the segment pairs are similar and thedimensions therebetween are such that the armature contact 22 can neversimultaneously contact or engage either opposite pair of segments. Thetwo segments 24 and 26 may be electrically connected together, externalto the switch 10, to form a common or an armature connection through theswitch 10, and the two segments 25 and 27 may be electrically isolatedexternal of the switch 10 to form the two effectively stationarycontacts of the switch 10. In other words, the two wires 34 and 36 areelectrically connected to simulate the connection to the movablearmature 50 of the functional representation in FIGURE 4. The other twowires 35 and 37 simulate the connections to the two stationary contacts50 and 51.

' Just as the armature 52 in FIGURE 4 cannot simultaneously contact bothcontacts 50 and 51, so cannot the connection to the two segments 24 and26 simultaneously be in electrical contact with the connections to bothsegments 25 and 2'7 at the disc 23. The operation of the magnetic switchIt), in this manner, simulates the electrical break-before-makeoperation of the transfer switch shown in FIGURE 4.

The acute angle formed by the internal surface of either pair of twoadjacent segments may be between 55 degrees and 60 degrees. Theparticular angle is selected to reduce any bounce of the armaturecontact 22. By making the angle acute, a slight skid is developed by thearmature contact 22 as it wedges between the two adjacent internalsurfaces. It the acute angle is made larger, the contact 22 hits thesegment surfaces with a smaller skidding effect so that any tendency tobounce is increased. The more closely is the contacted segment surfacealigned to be perpendicular to the direction of motion of the contact22, the greater the bounce. Bounce is harmful because of the noise itintroduces and because the timing of the switch becomes less accurate.By providing for an acute angle between the internal surfaces of thesegments 24 and 25, the contact 22 wedges therebetween as it is moved onthe armature so that any tendency to bounce is resisted.

In order to maintain the timing accuracy of the switch, there is apractical lower limit to the size of the acute angle formed by theadjacent internal surfaces of the segment pairs. As the acute angle ismade smaller, the tolerances for the contact swing become greaterbecause it is more difiicult to predict the exact point on the internalsurface which will first engage the contact 22. By making the angle moreacute, the dimension of the internal surface in the direction of thecontact swing is greater and a small ecentricity in the contact swingvaries the duration of the switching operation by a considerable factor.With a stroke of 0.001 inch given as an illustration above, theswitching interval responsive to a change of the magnetic flux throughthe armature 15 may be approximately 200 microseconds. The moreperpendicular are the alignments of the contacted internal surfaces withthe direction of the movement of the contact-22, the less variation inthe switching interval and, therefore, the more acurate the timingprovided by the switch 10. The particular angle which is selected is,therefore, a compromise to both reduce bounce and maintain smalltolerances in the timing of the switch 10.

As described above, shells 11 and 12 serve as a magnetic shield for thecomponents enclosed thereby, namely the segments 24-27, holes 40, andwires 34 to 37. The shells 11 and 12 serve to prevent magnetic noisepulses from being induced to the contacts of the switch It) and toreduce any tendency for such pulses to initiate current flow in theelectrical circuitry of the switch 10. Noise pulses are also not readilyintroduced by capacitive or electrical coupling to the armature 15because it is electrically insulated from the electrical circuitsthrough the switch 10. The contact insulator 10 prevents any electricaldisturbances introduced to the armature 15 either by capacitive couplingwith the casing 13 or by electrical contact therewith from beingintroduced to the segments 24 through 27 of the contact disc 23. Withthe armature 15 isolated in this manner from the electrical circuitry, anoise level ilustratively as small as 10 microvolts is present. The 10microvolt illustrative noise level represents the total noise level dueto all factors including due to bounce and stray capacity. Signals, forexample, as low as microvolts may accordingly be switched by the switch10 and readily separated from the noise.

Although this invention has been disclosed and illustrated withreference to particular applications, the principles involved aresusceptible of numerous other applications which will be apparent topersons skilled in the art. The invention is, therefore, to be limitedonly as indicated by the scope of the appended claims.

I claim:

1. In a switching unit, a casing forming an envelope for the switchingunit and having a cylindrical armature enclosing section, and acylindrical contact enclosing section aifixed to said armature enclosingsection and concentrically positioned with respect to said armatureenclosing section, a cylindrical armature made of magnetic material andenclosed by said armature enclosing section, a resilient pivot supportfor said armature and permitting the pivotable movement of said armaturein a first plane by magnetic flux through said armature enclosingsection, an insulator member carried at one end of said armature, anarmature contact carried by said insulator and enclosed by said contactenclosing section and insulated by said insulator from said armaturewhereby said armature is electrically isolated from the contacts of theswitching unit, and a number of segments of con-' ductive materialdisposed in a second plane displaced angularly from the first planeencircling said armature contact and defining the stationary contacts ofthe switching unit.

2. In a switching unit, a casing forming an envelope for the switchingunit and having a cylindrical armature enclosing section, and acylindrical contact enclosing sec.- tion and concentrically positionedwith respect to said armature enclosing section, a cylindrical armaturemade of magnetic material and enclosed by said armature enclosingsection, a resilient support for said armature and permitting themovement of said armature in a first plane by magnetic flux through saidarmature enclosing section, an insulator member carried at one end ofsaid armature, an armature contact carried by said insulator andenclosed by said contact enclosing section and insulated by saidinsulator from said armature whereby said armature is electricallyisolated from the contacts of the switching unit, a first pair ofconductive segments positioned in substantially a second single planedisplaced angularly from the first plane in said contact enclosingsection adjacent said armature contact for simultaneous contact therebywhen said armature is in one position, a second pair of conductivesegments positioned in substantially the second single plane in saidcontact enclosing section adjacent said armature contact forsimultaneous contact thereby when said armature is in a second position,a common electrical conductor electrically connected to one of saidsegments of said first and of said second pairs of contacts, anelectrical conductor electrically connected to the other segment of saidfirst pair, and an electrical conductor electrically connected to theother segment of said second pair.

3. A magnetic switch, including, a movable armature having a normal andan operative position, a contact affixed at one end of said armature,and a contact member including four contact segments which are insulatedfrom each other, said four segments defining a diamondshaped centrallylocated opening in which said armature contact is positioned, saidarmature contact being positioned adjacent one of the two acute anglesof the diamond-shaped opening against two of said contact segments whensaid movable armature is in its normal position and adjacent the otheracute angle of the diamondshaped opening when said movable armature isin its operative position.

4. A magnetic switch, including, a movable armature having a normal andan operative position, a contact afiixed at one end of said armature,and a contact member including four contact segments which are insulatedfrom each other, said four segments defining a diamond-shaped centrallylocated opening in which said armature contact is positioned, saidarmature contact being positioned adjacent one of the two acute anglesof the diamond-shaped opening against two of said contact segments whensaid movable armature is in its normal position and adjacent the otheracute angle of the diamondshaped opening when said movable armature isin its operative position, the distance between the contact segmentsoppositely positioned about said armature contact being greater than themaximum cross sectional distance of said armature contact so that saidarmature contact cannot simultaneously contact a pair of oppositelypositioned contact segments.

5. A magnetic switch, including, a movable armature having a normal andan operative position, a contact affixed at one end of said armature, aninsulator member having four conductive connections passing through saidmember, and a contact member including four contact segments which areinsulated from each other, said contact member being afiixed to saidinsulator member so that each of said contact segments is in electricalcontact with a different one of said conductive connections through saidinsulator member, said four segments defining a diamond-shaped centrallylocated opening in which said armature contact is positioned, saidarmature contact being positioned adjacent one of the two acute anglesof the diamondshaped opening against two of said contact segments whensaid movable armature is in its normal position and adjacent the otheracute angle of the diamond-shaped opening when said movable armature isin its operative position.

6. In a switching unit, a casing forming an envelope for enclosing thevarious components of the switching unit including a portion made ofmagnetic material and a portion made of non-magnetic material, anarmature made of magnetic material positioned in the non-magneticportion of said casing, said armature having a normal position when notunder the influence of a magnetic field and an operative position whenunder the influence of a magnetic field, a contact insulator supportedby said armature, a movable contact supported by said contact insulatorand insulated by said contact from said armature, said armature contactbeing movable with said armature and therefore having a normal positionand an operative position, and a contact member including four contactsegments which are insulated from each other, said four segmentsdefining a diamond-shaped centrally l0 cated opening in which saidarmature contact is positioned, said armature contact being positionedadjacent one of the two acute angles of the diamond-shaped openingagainst two of said contact segments when said movable armature is inits normal position and adjacent the other acute angle of thediamond-shaped opening whe said movable armature is in its operativeposition, said armature contact and said four segments of said contactmember being positioned in the magnetic portion of said casing so as tobe shielded thereby from external magnetic fields.

7. A magnetic switch, including, a movable armature having a normal andan operative position, a contact afiixed at one end of said armature,and a contact disc including four contact segments which are insulatedfrom each other, said four segments defining a diamond-shaped centrallylocated opening in which said armature contact is positioned, saidarmature contact being positioned adjacent one of the two acute anglesof the diamondshaped opening against two of said contact segments whensaid movable armature is in its normal position and adjacent the otheracute angle of the diamond-shaped opening when said movable armature isin its operative position, said armature contact being tapered havingthe shape of a truncated cone so that the stroke of said armaturecontact between the pairs of contact segments is determined by theposition of the armature contact along its longitudinal axis withrespect to the position of said contact disc.

References Qitetl in the tile of this patent UNITED STATES PATENTS2,298,802 Meyerhoefer Oct. 13, 1942 2,402,744 Horman Sept. 17, 19462,541,398 Wood Feb. 13, 1951 2,886,668 Steward et al. May 12, 19592,908,780 Walters Oct. 13, 1959 2,914,634 Koda Nov. 24, 1959 2,921,161Scata et al. Jan. 12, 1960 2,931,871 Dowds Apr. 5, 1960 2,976,379 RhodesMar. 21, 1961 3,001,046 Racz et al. Sept. 19, 1961 3,014,106 JenningsDec. 19, 1961

3. A MAGNETIC SWITCH, INCLUDING, A MOVABLE ARMATURE HAVING A NORMAL AND AN OPERATIVE POSITION, A CONTACT AFFIXED AT ONE END OF SAID ARMATURE, AND A CONTACT MEMBER INCLUDING FOUR CONTACT SEGMENTS WHICH ARE INSULATED FROM EACH OTHER, SAID FOUR SEGMENTS DEFINING A DIAMONDSHAPED CENTRALLY LOCATED OPENING IN WHICH SAID ARMATURE CONTACT IS POSITIONED, SAID ARMATURE CONTACT BEING POSITIONED ADJACENT ONE OF THE TWO ACUTE ANGLES OF THE DIAMOND-SHAPED OPENING AGAINST TWO OF SAID CONTACT SEGMENTS WHEN SAID MOVABLE ARMATURE IS IN ITS NORMAL POSITION AND ADJACENT THE OTHER ACUTE ANGLE OF THE DIAMONDSHAPED OPENING WHEN SAID MOVABLE ARMATURE IS IN ITS OPERATIVE POSITION. 